[Dovecot] variable expansion in dovecot.conf?

[OpenMacNews]

hi all,

does dovecot.conf support the definition/use of user variables?

e.g., in principle,

    my_DIR = /path/to/something/

then,

    default_mail_env = maildir:${my_DIR}/%d/Accounts/%1u/%u/Maildir

or, for that matter,

        default_mail_env = blahblah

then,

    namespace private {
        ...
        location                 = $default_mail_env
        ...


i finallly figured out -- through randon thrashing -- that the simple "$" 
format has been causing me grief ...

and, cursory searching has not dug up anything (yet) in the man/wiki/etc.

possible? reference docs for it?

thx!

(ack to my margarita for now ...)

richard